This invention relates to imaging with a compound aperture. In particular, speckle reduction is provided by imaging with the compound aperture.
Speckle noise is generated in images associated with phased arrays. Speckle varies as a function of various imaging parameters. For example, speckle varies as a function of temporal frequency and spatial frequency. As a result, speckle is reduced by compounding temporal frequencies (frequency compounding) and spatial frequencies (spatial compounding). For example, image information responsive to two different frequencies is compounded. Compounding the image information averages or reduces the speckle contribution for the resulting image.
One method of spatial compounding uses different steering angles or scan line angles. Two different sets of image information representing a same general or overlapping area are acquired. Each set is responsive to a different steering angle. For each given spatial location, data is acquired in response to transmissions and receptions along a scan line that intersects the location at different angles. The sets of data associated with a common or overlapping region are compounded to reduce speckle. Each frame of data is acquired before the steering angle is changed for acquiring another frame of data, resulting in registration errors for moving objects or associated with movement of a transducer. Speckle reduction may not be provided for non-overlapping areas of the two images.
The present invention is defined by the following claims, and nothing in this section should be taken as a limitation on those claims. By way of introduction, the preferred embodiment described below includes a method and system for imaging with a compound aperture.
Using the same scan lines, different transmit and/or receive apertures are used to obtain data. Speckle patterns associated with different transmit or receive apertures decorrelate. By compounding the obtained data, speckle noise maybe reduced.
In one aspect, a method for imaging with a compound aperture is provided. First data representing a first scan line in response to a first aperture is obtained. Second data representing the first scan line and responsive to a second aperture is obtained. A center of the second aperture is at a different position along an array of elements than a center of the first aperture. The first and second data is detected and then combined.
In a second aspect, another method for imaging with a compound aperture is provided. First and second data representing a same plurality of scan lines is obtained. The first and second data is obtained without purposeful movement of the transducer. The first and second data are detected and then combined. An image is generated from the combined data where the image represents the plurality of scan lines. The first and second data are responsive to a same focal depth and apertures with different positions.
In a third aspect, a system for imaging with a compound aperture on a transducer array of a plurality of elements is provided. A multiplexer is operable to sequentially set first and second apertures for a first scan line. A center of the second aperture is at a different position along the transducer array than a center of the first aperture. A detector detects the first and second data responsive to the first and second apertures, respectfully. A summer combines the first and second detected data.
Further aspects and advantages of the invention are discussed below in conjunction with the preferred embodiments. These further aspects are claimed or maybe later claimed.